Various embodiments relate in general to detecting statistical characteristics of a lighting device. These are to be understood, for example, as operating hours or switching-on processes of the lighting device. The reason for this measure resides in the fact that, for example, the light yield of LEDs depends strongly on ageing. By way of example, it is then possible to change the driving of the LEDs as a counter measure, depending on the detected operating hours. As regards defective returns, the number of operating hours or the number of switching-on processes is an important criterion in determining the cause of failure. In critical fields of application of lighting devices, for example OP luminaires, traffic lights, street lamps, maintenance intervals can be complied with after detection of the operating hours or the switching-on operations, it being possible thereby for failures of the lighting device that are fraught with consequences to be virtually completely prevented.
Different storage devices, for example flash memories, E2Proms, hard disks, etc are used in the prior art to detect such statistical characteristics. In this case, flash memories constitute the most advantageous variant, but are associated with the disadvantage that they cannot be written to as frequently as the other storage media. It is typically possible to write to flash memories up to approximately 50 000 times. E2Proms, which are, however, substantially more expensive than flash memories, offer the advantage that they permit up to 500 000 write cycles. On the one hand, as storage media hard disks require to be brought up to speed in order to carry out a write operation, something which is associated with time and energy requirement, and on the other hand are themselves expensive in small quantities.
The shorter the time unit that is to be detected is selected, for example hours or seconds, the more frequently the write cycles need to be carried out, and the more stringent the requirements placed on the selected storage medium. Moreover, there is also the problem that, as regards switching off the lighting device, the internal supply must be maintained for a sufficiently long time such that the characteristic can be secured. This is associated with the further disadvantage that large and therefore expensive buffer capacitors must be made available for supplying the components essential to the storage operation.